Balanced orientated flexible packaging composite

ABSTRACT

A laminated packaging film is disclosed. This film composed, in order, of an outer layer of balanced biaxially-oriented polyamide, a flexible metal foil, a layer of balanced biaxially-oriented polypropylene and an inner layer of heat-sealable polyolefin -- is readily produced and yields an exceptionally strong and flex-resistant laminate useful inter alia for the production of pouches and like, liquid containers of large volume.

INTRODUCTION TO THE INVENTION

An object of this invention is the production of self-sealing, packagingfilm laminate of high strength.

Another object of this invention is the provision of the various layersof the composite packaging film in a sequence which provides maximuminterlayer cooperation while simplifying the manufacture of the film.

A further object of this invention is the production of thin packagingfilms of exceptionally high flex-resistance, useful as containers forlarge volumes of liquid materials.

A particular object of this invention is the provision of a flexible,packaging film which can be self-sealed into pouches which, while easilytransported in essentially flat, compressed form, are capable ofretaining 5 to 20 or more liters of liquid contents without succumbingto the physical stress due to movement or shift of liquid contentswithin a container during transit and use.

These, and other objects of the invention as are described hereinafter,are obtained through the present invention.

DESCRIPTION OF THE INVENTION

This invention relates to the production of a laminate or compositepackaging film of highly improved properties.

It has long been sought to produce a laminated film which will be usefulin a pouch or like packaging construction for the transport and storageof liquids. Although cans and other containers of fixed dimensions havelong been employed for use with large volumes of ketchup, syrup and thelike, these rigid containers have many drawbacks.

Because they are rigid in dimension, they must be unusually strong towithstand the physical stress due to shifts in their liquid contents.This is particularly true with the large volume of from 5 to 20 literspreferred in accordance with this invention. In addition, their fixed,heavy construction makes them uneconomical to transport unless filled.Even when empty, they occupy their full volume. Therefore, they aredesirably produced close to the site of filling and used only once.

This invention makes possible the provision of light, pouches or likeflexible containers for the packaging of similar volumes of liquidmaterial. The flexibility of these films -- even in container form --permits much of the physical stress due to shifts in liquid contents tobe absorbed through movement of the container wall. This permits thecontainers to be composed of material of significantly lower strengthand weight than those employed in rigid containers.

In addition, the containers formed of the present films can becompressed into essentially flat form when empty. This greatlyfacilitates their storage, transport and reuse.

The films of this invention are composed of four essential layers orlaminated plies. These layers are (in order, from the outside to theinside of a packaging wall):

1. balanced biaxially-oriented polyamide;

2. flexible metal foil;

3. balanced biaxially-oriented polypropylene; and

4. heat-sealable polyolefin.

When affixed together, preferably through the use of various sealers andadhesives, these four layers produce a composite, laminate film ofunusually high strength and flex-resistance.

The outermost layer of this film is composed of polyamide which has beenbiaxially-oriented. By being biaxially-oriented in essentially balanceddegree, this layer provides substantial flex-crack resistance. Inaddition, the balanced biaxial orientation of the nylon yields a strongresistance to burst or tearing.

This layer, which may be composed of essentially any of the polyamidesknown in the art, although nylons are particularly preferred. It isnecessary only that they have been stretched to provide a balancedbiaxial orientation. This layer may be provided in a thickness of from0.0003 to 0.003 inch, preferably about 0.0006 inch. Such a thicknessprovides a strong outer covering to the present composite, packagingfilms.

The second, essential layer may be composed of any of the flexible metalfoils known in the art. These foils -- such as lead, copper, andpreferably aluminum -- are ordinarily from 0.0002 to 0.002, preferablyabout 0.00035 inch in thickness. In addition to providing excellentprotection from ultra-violet light, these films have a high resistanceto vapor penetration and provide an excellent barrier to penetration ofliquid, particularly water or moisture, through the film.

The third essential layer comprises balanced biaxially-orientedpolypropylene. This is also a highly flex/crack resistant material. Itmay be composed of any of the polypropylenes known in the art and whichhave been stretched to produce the desired balanced,biaxial-orientation.

This biaxial polypropylene layer may have a thickness of from 0.0003 to0.002, preferably about 0.0005 inch. As such, it additionally acts as ahighly inert barrier which protects and restrains the contents of theeventual pouch.

The fourth and innermost essential layer of this invention is composedof heat-sealable polyolefin. This olefin layer may be composed, forexample, of polyethylene or polypropylene (preferably of medium density)and provides a barrier through which the present films may be sealed toproduce pouch-like containers. This layer should be provided at athickness of from 0.001 to 0.004, preferably about 0.002 inch. In thismanner, ready sealability, as well as substantial contribution to theimpermeability of the film as a whole is obtained.

Although virtually any heat-sealable polyolefin may be utilizedherewith, highly temperature resistant polyolefin, particularlypolyethylene is preferred. Thus, for example, medium densitypolyethylene having a melting point of from about 70° to 90° C so as topermit its hot fill application to the film at temperatures of fromabout 85° to 95° C is preferred.

The unique physical characteristics of this film are believed partiallyattributable to the instant provision of balanced, biaxial polymerlayers on both sides of the metal foil. Metal foils are particularlysusceptible to cracking and pinhole breaks incident to flex. The presentarrangement of different balanced biaxially-oriented polymers on thesides of the foil, however, is believed to allow cooperation whichprotects this sandwiched metal foil so as to increase its resistance toflexing and extend the useful life of the film.

By whatever mechanism, however, the present films possess exceptionalphysical characteristics which permit their substitution for thesubstantially stronger materials employed in prior art rigid containers.Also, they solve the major problem which has heretofore limited theutility of flexible films. The films of this invention successfullyresist the cracking of foil and rupture of laminate which haveaccompanied past attempts to package substantial volumes of liquid innon-rigid containers.

In addition to these four essential layers of the present film, certainoptional layers or treatments have been discovered further to enhanceits strength and durability. These additional layers or treatments maybe utilized, either individually or in combination, further to improvethe characteristics of the present packaging films.

One optional layer is a primer coat which may be applied to the internalsurface of the biaxially-oriented polyamide layer. This layer, which ispreferably from about 0.00005 to 0.0002 inch in thickness, improves theinternal film adhesion to the nylon layer. It may be composed of any ofthe primers known in the art, but most desirably comprises apolyethylene imine.

A second layer desirably interposd between the balancedbiaxially-oriented nylon and the metallic foil comprises a conventionaladhesive resin. This resin, which desirably is from about 0.0003 to0.001 inch in thickness, should directly contact the metal foil toprovide improved adhesion thereto. The resin is preferably an ethyleneacrylic acid polymer and most preferably is utilized in conjunction withthe aforementioned primer for the biaxially-oriented nylon.

On the other side of the metallic foil (and between the metallic foiland the biaxially-oriented polypropylene) there is desirably provided avinyl washcoat on the inner surface of the foil. This coat, which mostdesirably is in the thickness of from about 0.00005 to 0.0002 inch,increases the chemical resistance of the foil so as further to improveits barrier characteristics.

An adhesive resin coating is also preferred between the aluminum foiland the balanced biaxially-oriented polypropylene. This coating, whichis preferably a urethane polymer provided in the thickness of from0.00005 to 0.0002 inch, should directly contact the biaxially-orientedpolypropylene so as to improve the adhesion of the film layers. Mostpreferably, this adhesive is utilized in combination with theaforementioned vinyl washcoat for the aluminum foil.

Still a further layer of adhesive resin is preferably provided betweenthe balanced biaxially-oriented polypropylene and the heat-sealablepolyolefin layer. This resin is also preferably composed of polyurethanein a thickness of from about .00005 to .0002 inch. Again it contributesto the internal film adhesion by providing protection againstlamination.

It is also desirable to treat various of the layer surfaces further toimprove the adhesion and integrally of the present film. The balancedbiaxially-oriented polypropylene layer, for example, is preferablytreated on at least one surface to reduce its slip characteristics. Thismay be accomplished in conventional fashion by, for instance,application of an anti-slip agent. Further improvement in the film maybe obtained by subjecting the internal film surfaces of the polyamideand polyolefin layers to corona discharge.

The layers of this invention, whether or not including one or more ofthe optional layers of this invention, may readily be laminated to formthe present composite, packaging films. This lamination may be performedby any of the means well-known in the art. A particular sequence oflamination is preferred, however, because it greatly facilitatesmanufacture of tightly adherent, high strength films.

This preferred sequence of lamination involves the production of twosub-laminates which may then be adhered together to produce films of thepresent invention.

The first sub-laminate is composed of affixed layers of balancedbiaxially-oriented polyamide and metallic foil. Most desirably, thissub-laminate is produced by extruding a layer of adhesive resin, such asethylene acrylic acid polymer, between these two preformed, essentiallayers. This produces a sandwiched material of high strength.

It is further preferred that, preliminary to the extrusion lamination,the biaxially-oriented polyamide be treated by corona discharge so as toimprove the adhesion to the aluminum foil. In addition, if a primer coatis to be provided in the laminate, this coating should be applieddirectly to the polyamide, or corona-treated polyamide surface, prior toextrusion.

If the composite, packaging is also to include the preferred washcoatover the inner metallic foil surface, this coat may be applied to thefirst sub-laminate at any time prior to or following extrusion. It ispreferred, however, that it be coated onto the metallic foil afterformation of the sublaminate.

The second sub-laminate is composed of the balanced biaxially-orientedpolypropylene and heat-sealable layers. These two layers are affixedtogether -- preferably through application of a resin adhesive -- toform the sub-laminate. Still further to improve the adherence betweenthese two layers, it is preferred that the polyolefin internal filmsurface be subjected to corona discharge and the biaxial polypropylenesurfaces treated with an anti-slip agent before they are affixedtogether.

After formation of the two sub-laminates, they may be joined together byapplication of heat and pressure. Again, the integrity of the composite,packaging film is improved if an adhesive, such as polyurethane polymer,is coated on one or both of the surfaces to be joined preparatory to theapplication of heat and pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present invention is more completely describedby reference to the accompanied drawings wherein:

FIG. 1 is a side view showing the film of the present invention havingonly its four, essential film layers;

FIG. 2 is a side view showing a film of the present invention whichincludes both the four essential layers and the various optional layerstherefor;

FIG. 3 is a plain view showing a pouch composed of the packaging film ofthe present invention; and

FIG. 4 is a partial cross-sectional view of a pouch composed of twoadherent packaging films of the present invention.

DESCRIPTION OF THE DRAWINGS

With reference to FIGS. 1 and 2, composite, packaging films of thepresent invention are depicted as laminates 1 and 11, respectively. InFIG. 1, only the essential layers of this invention are disclosed, theselayers being an outside layer of balanced biaxially-oriented polyamide2, a metal foil 5, a layer of balanced biaxially-oriented polypropylene8 and a layer of heat-sealable polyolefin 10.

The packaging film 11 depicted in FIG. 2 depicts both the essentiallayers (also shown in FIG. 1) and various optional layers alreadydescribed herein. These essential layers 2, 5, 8 and 10 are of the samecompositions as previously described with respect to FIG. 1. Inaddition, however, there is depicted a primer coat 3; and a layer ofadhesive resin 4; a vinyl washcoat 6; and two additional layers ofadhesive resin 7 and 9.

With reference to FIG. 3, there is illustrated a pouch formulated fromtwo composite, packaging films of this invention. The pouch 21 iscomposed of the two separate packaging films 26 and 27 (shown inexpanded form as it would exist if the pouch were filled). The perimeterof the pouch 21 is indicated to comprise a sealed perimeter portion 25(composed of joined layers 26 and 27) by which the contents of the pouchare defined. A screw top spigot 28, is located in the surface of onefilm 27 as a means for filling and emptying the pouch of its liquidcontents.

FIG. 4 illustrates a cross-sectional view of a portion of the pouch ofFIG. 3. This disclosed portion represents the perimeter and partiallyinterior view of the pouch walls. The opening 29 within the pouch showsa degree of expansion of the pouch within which the liquid contentswould be held. Also shown is the orientation of the two packaging films30 and 30' so that two separate film layers of heat-sealable polyolefin10 and 10' are contingent and bondable, one to the other, so as to forma single, double thickness of heat-sealed polyolefin 31 at the perimeterof the pouch. The remaining layers 2, 5 and 8 of film 30 and 2', 5' and8' of film 30' are of the same compositions as previously described withrespect to FIG. 1.

The pouch depicted in FIG. 3 in plain view and in FIG. 4 incross-section is formed from two of the packaging films of the presentinvention. These pouches are conveniently prepared by laying one sheetdirectly over the other and applying heat and pressure only about theouter perimeter of the overlapping films so as to form a heat-sealedjoint surrounding the pouch. In this manner, and particularly if asdepicted in FIG. 3 a spout or like device has been placed in the body ofone of the two films at a distance spaced from the peripheral,heat-sealed edges, an enclosed pouch or package having a singlecloseable opening is produced. This pouch permits easy transportation incompressed form and ready filling with a liquid material which expandsat the opening remaining within the pouch.

In an alternate embodiment, now shown, a pouch similar to that depictedin FIGS. 3 and 4 may be formed from a single sheet of film. Thus, asingle sheet of film may be folded 180° at its mid-point and thenheat-sealed at its outer perimeter to form a unitary pouch. It willdiffer from the pouch of FIG. 3 in that one of its edges will be offolded construction.

Certain changes or modifications in the practice of the presentinvention can be readily entered into without substantially departingfrom the intended spirit and scope. Therefore, it is to be fullyunderstood that the invention is not to be limited or in any wayrestricted by the preferred embodiments and the drawings in theforegoing specification. Rather, the scope of this invention is to beinterpreted and construed in the light of what is set forth anddelineated in the appended claims.

I claim:
 1. A composite, flexible packaging film comprising essentiallya first layer of balanced-oriented polyamide, providing substantiallyflex-crack resistance, affixed to one side of a second layer of flexiblemetal foil and a third layer of balanced biaxially-orientedpolypropylene, also providing substantially flex-crack resistance,affixed to the opposite side of said foil and to a fourth layer ofheat-sealable polyolefin.
 2. The film of claim 1, wherein the polyolefinlayer comprises polyethylene.
 3. The film of claim 2, wherein thepolyethylene has a melting point of from about 70° to 90° C.
 4. The filmof claim 1, wherein the balanced biaxially-oriented polypropylene andpolyethylene layers are affixed together through an intermediate layerof adhesive resin.
 5. The film of claim 4, wherein the adhesive resin ispolyurethane.
 6. The film of claim 1, wherein the foil is provided witha vinyl washcoat on the side adjacent the balanced biaxially-orientedpolypropylene layer and is affixed to said polypropylene layer through alayer of adhesive resin.
 7. The film of claim 6, wherein the adhesiveresin comprises polyurethane.
 8. The film of claim 1, wherein thebalanced biaxially-oriented polyamide layer is provided with a primercoat of polyethylene imine on the side adjacent the metal foil and isaffixed to said foil through a layer of adhesive resin.
 9. The film ofclaim 8, wherein the adhesive resin comprises ethylene vinyl acetatecopolymer.
 10. A flexible pouch composed essentially of the film ofclaim 1, said pouch being self-sealed through the fourth layer ofheat-sealable polyolefin at overlapping edge portions of said film so asto define an internal pouch cavity of at least 5 liters in volume.